One source of an understanding of the state of the art of fiber optic sensors is a publication, entitled "Fiber Optic and Laser Sensors II" PROCEEDINGS OF SPIE--The International Society for Optical Engineering, Volume 478, 385-12 through 385-18, May 1-2, 1984. As noted therein, two general classes of sensors are known, the first being based on an optical reflection technique and the second being a microbend technique.
The former technique is not force-responsive, i.e., it is not operative based on mechanical stress applied to an optical fiber.
The latter technique looks to the use of a relatively inflexible optical fiber and the detection of directing of light from the fiber core into the fiber cladding upon distortion of the force-responsive optical fiber. Fiber optic sensors of force-responsive variety using a relatively inflexible optical fiber and based on the microbending technique are shown in U.S. Pat. Nos. 4,420,251, 4,408,829, 4,860,586 and 4,918,305.
A further version of a force-responsive fiber optic sensor is seen in U.S. Pat. No. 4,750,796, which looks not to microbending of a relatively inflexible optical fiber, but to the use of a quite flexible optical fiber, being comprised of a core and cladding, both formed of an elastomeric material. A similar fiber optic sensor is shown in U.S. Pat. No. 4,830,461.
In the particular area of air bag control, which is a preferred area of interest of the subject invention, note is taken of U.S. Pat. No. 4,988,862. Therein, an air bag actuation is caused to occur when an optical fiber is broken and light communication between a transmitter and a receiver is fully interrupted.